Spontaneous Bubbling at Porous Hydrophobic Membranes

Abstract

IT has been observed that when a hydrophobic membrane permeable to gases is present at the interface between water and a dry gas, the gas passes through the membrane and is released in the liquid as bubbles. The interesting feature of this process is that it proceeds without the need to raise the pressure of the gas and will even operate against a positive hydrostatic head of liquid. Indeed, substantial static pressures are developed in the water chamber when escape of the gas is prevented on the liquid side of the membrane. The membrane used in these experiments was a 7-mil thick, extruded tetrafluoroethylene (TFE) film which, in the course of preparation, was never subjected to temperatures above 300° C. The morphology and pore size of the film have not as yet been determined.